MidTerm03

The primary reason that Venus is much hotter than the Earth today is:

a. The greenhouse effect is much stronger on Venus.
b. Venus has a much thicker ozone layer than the Earth does.
c. Venus is much more volcanically active.

a.

How would the temperature of the Earth change if there were no greenhouse effect?

a. the temperature would not change
b. Earth would be much hotter
c. Earth would be much colder

c.

Which of the gases below contribute to the greenhouse effect on Earth?

a. ozone
b. oxygen
c. carbon dioxide
d. more than one of the above

c.

In nuclear reactions in the Sun, four nuclei of __________ combine to make a single nucleus of __________.

a. helium; hydrogen
b. hydrogen; helium
c. carbon; helium
d. protonium; hydrogen

a.

Fusion takes place in what part of a star?

a. the extended outer atmosphere (corona)
b. the surface (photosphere)
c. the core

c.

Stars exist because of the hydrostatic equilibrium between __________ and __________.

a. gravity pulling inward; pressure pushing outward
b. gravity pushing outward; pressure pulling inward
c. pressure pushing outward; pressure pulling inward
d. explosions in the core pushing outward; space pulling inward

a.

Which of the following can one NOT directly measure from the spectrum of a star?

a. composition of the star
b. temperature of the star
c. radius of the star

c.

Which of the properties below is typically the most difficult to measure for a star? HINT: Which requires the most observations:

a. composition
b. distance
c. temperature
d. brightness

b.

Since all stars begin their lives with the same basic composition, what characteristic most determines how they will evolve after their formation?

a. The time period they are formed with.
b. The mass they are formed with.
c. The brightness they are formed with.
d. The location where they are formed.

b.

The luminosity of a star is:

a. How bright the star appears to be when you look at it.
b. A combination of how bright the star appears to be when you look at it and how far away the star is.
c. Completely determined only by the temperature of the star.
d. The amount of energy the star releases every second.

d.

The light you see from a distance star appears dimmer than the light coming from the same star would if you were closer to it because the light __________ as it moves through space.

a. loses energy
b. spreads out
c. slows down
d. changes wavelength

b.

Imagine you are in a spaceship. You observe the Sun while near the Earth, then fly to a point much farther from the Sun. You repeat your observations. When you compare the two observations you will find that the __________ of the Sun changes.

a. brightness
b. luminosity
c. temperature
d. composition

a.

Imagine two stars called A and B. Both stars have the same temperature and composition, but not the same diameter. From this, you can conclude that:

a. Both stars definitely have the same luminosity, no matter what their diameters are.
b. The star with the larger diameter will be more luminous.
c. The star with the smaller diameter will be more luminous.
d. Either star could be more luminous, but temperature and diameter of the stars have nothing to do with it.

b.

Parallax is used to measure the __________ a star.

a. color of
b. angle to
c. distance to
d. size of
e. composition of

c.

Imagine we could place a telescope on Jupiter, which is about 5x farther from the Sun than the Earth is (in other words the orbit of Jupiter has a radius 5x bigger than the orbit of the Earth). The telescope on Jupiter would be able to measure parallax for stars __________ than a similar telescope on Earth could.

a. 5x closer
b. 5x farther
c. 10x closer
d. 10x farther

b.

What happens when a star exhausts its hydrogen supply?

a. Its core contracts, but its outer layers expand and the star becomes bigger and more luminous.
b. Its core and outer layers contract, becoming smaller and dimmer.
c. Its core and outer layers expand, becoming bigger but dimmer.
d. Its core expands, but its outer layers contract and the star becomes smaller and hotter.

a.

Compared to the main sequence star it evolved from, a red giant is:

a. Cooler, less luminous, and about the same mass.
b. Hotter, less luminous, and more massive.
c. Hotter, more luminous, and about the same mass.
d. Cooler, more luminous, and about the same mass.
e. The same temperature, same luminosity, and more massive.

d.

Why does a star grow larger after it exhausts the hydrogen in its core?

a. Helium fusion in the core generates enough pressure to push the upper layers outward.
b. Helium fusion in the shell outside the core generates enough pressure to push the upper layers outward.
c. Hydrogen fusion in a shell outside the core generates enough pressure to push the upper layers outward.
d. The internal radiation generated by the hydrogen fusion in the core has heated the outer layers enough that they can expand even though the star is no longer fusing hydrogen.
e. The outer layers of the star are no longer gravitationally attracted to the core.

c.

The trend on the HR diagram shows the path of a star during part of its evolution. During this time the star is getting:

a. smaller and hotter
b. smaller and cooler
c. larger and hotter
d. larger and cooler

d.

What age would a bluer star cluster be relative to a redder star cluster?

a. younger
b. older
c. same age
d. impossible to determine

a.

What will happen to the 1-solar-mass star at the end of its life?

a. It will explode in a supernova.
b. It will collapse to make a neutron star.
c. It will gain mass until it collapses under its own weight.
d. It will eject a planetary nebula.
e. It will begin burning carbon in its core.

d.

Which of the following sequences correctly describes the stages of life for a low-mass star?

a. white dwarf, main-sequence, red giant, planetary nebula, protostar
b. protostar, main-sequence, white dwarf, red giant
c. protostar, main-sequence, red giant, planetary nebula, white dwarf
d. planetary nebula, protostar, red giant, main-sequence, white dwarf
e. red giant, protostar, main-sequence, white dwarf, planetary nebula

c.

The lifetime of a star half the mass of the Sun is __________ that of the Sun?

a. much shorter than
b. the same as
c. much longer than

c.

What is a planetary nebula?

a. A disk of gas surrounding a protostar that may form into planets.
b. What is left of the planets around a star after a low-mass star has ended its life.
c. The expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star.
d. The expanding shell of gas that is left when a white dwarf explodes as a supernova.
e. The molecular cloud from which protostars form.

c.

What happens to the core of a star after a planetary nebula occurs?

a. It becomes a white dwarf.
b. It breaks apart in a violent explosion.
c. It contracts from a protostar to a main-sequence star.
d. It becomes a neutron star.
e. None of the above.

a.

Which of the following is closest in mass to a white dwarf?

a. Fargo-Moorhead
b. Earth
c. Jupiter
d. the Sun
e. the Moon

d.

Which of the following is closest in size to a white dwarf?

a. Fargo-Moorhead
b. Earth
c. Jupiter
d. the Sun
e. the Moon

b.

White dwarfs are called so because:

a. it emphasizes the contrast with red giants
b. they are the end-products of small, low-mass stars
c. they are supported by electron degeneracy pressure
d. they are both very hot and very small
e. they are the opposite of black holes

d.

What types of stars end their lives with supernovae?

a. All stars that are red in color.
b. Stars that have reached an age of 10 billion years.
c. Stars that are at least several times the mass of the Sun.
d. Stars that are similar in mass to the Sun.
e. All stars that are yellow in color.

c.

What did astronomer Carl Sagan mean when he said that, "We are all made of star stuff?"

a. Earth formed at the same time as the Sun.
b. The Universe contains billions of stars.
c. Life would be impossible without energy from the Sun.
d. The carbon, oxygen, and many other elements essential to life were created by fusion in stellar cores.

d.

Which event marks the beginning of a supernova?

a. The onset of helium burning after a helium flash in a star with mass comparable to the Sun.
b. The beginning of neon burning in an extremely massive star.
c. The sudden collapse of an iron core into a compact ball of neutrons.
d. The expansion of a low-mass star into a red giant.
e. The sudden outpouring of X-rays form a newly formed accretion disk.

c.

Pulsars are composed of:

a. hydrogen
b. carbon and oxygen
c. neutrons
d. neutrinos

c.

Which of the following is closest in size (radius) to a neutron star?

a. basketball
b. the Sun
c. football stadium
d. city
e. the Earth

d.

The pressure holding up a white dwarf against gravity comes from:

a. fusion
b. heat leftover from a supernova explosion
c. electron degeneracy
d. neutrino convection

c.

Black holes form from the death of:

a. stars like the Sun
b. stars much less massive than the Sun
c. stars much more massive than the Sun

c.